USB: serial: ftdi_sio: don't access latency timer on old chips
The latency timer was introduced with the FT232BM and FT245BM chips. Do
not bother attempting to read or write it for older chip versions.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Johan Hovold <johan@kernel.org>
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index c540de1..7231473 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1406,6 +1406,9 @@ static int write_latency_timer(struct usb_serial_port *port)
int rv;
int l = priv->latency;
+ if (priv->chip_type == SIO || priv->chip_type == FT8U232AM)
+ return -EINVAL;
+
if (priv->flags & ASYNC_LOW_LATENCY)
l = 1;
@@ -1429,6 +1432,9 @@ static int read_latency_timer(struct usb_serial_port *port)
unsigned char *buf;
int rv;
+ if (priv->chip_type == SIO || priv->chip_type == FT8U232AM)
+ return -EINVAL;
+
buf = kmalloc(1, GFP_KERNEL);
if (!buf)
return -ENOMEM;